1. Field of the Invention
This invention relates generally to physiological electrodes which may be selectively connected to an appropriate lead line by means of a magnetic connector, and more specifically, this invention relates to disposable pre-gelled physiological electrodes which may be selectively connected to a desired instrument by means of a magnetic connector.
2. Description of the Prior Art
A particular type of physiological electrode used primarily for monitoring physiological functions (such as heart monitoring by cardioscope, electrocardiogram or electrocardiograph) has been designated as "snap-type". This designation arises from the fact that these disposable electrodes are connected to an appropriate lead wire by means of a "snap connection, which includes an upstanding stem on the electrode and a mating member on the lead that "snaps" over the stem.
While these "snap-type" electrodes have desirable features and have been widely utilized in the medical field, they also have a number of significant drawbacks. One of the most significant problems is that the snap connection may be inadvertently broken so that the electrical continuity between the instrument and the patient is broken. This problem becomes greater with time as the snap loses its resiliency and the mechanical snap connection becomes weaker.
Another problem relates to the so-called "motion artifact" that occurs when snap electrodes are utilized. This "motion artifact" is a distortion or breaking up of the electrical signal received from the patient and is generally associated with movement of the conducting lead from the electrode to the instrument. It seems likely that this "motion artifact" is related to relative movement between the upstanding stem and the mating snap member. Loss of resiliency with age probably aggravates this problem also. The obvious disadvantage of such "motion artifact" is that the representation of the physiological function being monitored is distorted.
Still another disadvantage of the conventional snap-type electrode is delay or difficulty in making the snap connection initially. In an emergency situation, inserting the mating snap member over the stem can result in the loss of valuable seconds. This is particularly true when the electrode is placed over an area having a substantial amount of subcutaneous fat, so that as pressure is applied to make the snap connection, the yielding of the fleshy portion may make it difficult or even impossible to make the snap connection.
Magnetic structures to form an electrical connector have been suggested in the past, and the use of magnetic material in making the connection between an electrode and a lead wire has also been suggested. However, none of the prior art approaches has effectively dealt with problems such as the desirability of utilizing conventionally available magnets, as opposed to specially formed magnets; the necessity of protecting ferromagnetic material from corrosion; the reduction of motion artifact; the necessity of preventing metal contact with the skin in longer term applications; and other difficulties to be overcome in making a practical, effective and cost-justified disposable electrode to be used with a magnetic connector.
Accordingly, there is a significant need for a disposable electrode that can be quickly and easily connected to and disconnected from an associated lead wire, that will minimize accidental disconnection but which may still be easily disconnected when desired, and that reduces undesired motion artifact. When made for use with a magnetic connector, such a physiological electrode should be capable of being used with a conventionally available magnet, should provide protection from corrosion for the ferromagnetic material, particularly in the presence of a corrosive material such as a saline gel, positively prevent metal contact with the skin in prolonged electrode applications, and be cost-competitive with snap-type electrodes.